Direct Substrate Delivery Into Mitochondrial Fission-Deficient Pancreatic Islets Rescues Insulin Secretion.

In pancreatic β-cells, mitochondrial bioenergetics control glucose-stimulated insulin secretion. Mitochondrial dynamics are generally associated with quality control, maintaining the functionality of bioenergetics. By acute pharmacological inhibition of mitochondrial fission protein , we demonstrate in this study that mitochondrial fission is necessary for glucose-stimulated insulin secretion in mouse and human islets. We confirm that genetic silencing of increases mitochondrial proton leak in MIN6 cells. However, our comprehensive analysis of pancreatic islet bioenergetics reveals that does not control insulin secretion via its effect on proton leak but instead via modulation of glucose-fueled respiration. Notably, pyruvate fully rescues the impaired insulin secretion of fission-deficient β-cells, demonstrating that defective mitochondrial dynamics solely affect substrate supply upstream of oxidative phosphorylation. The present findings provide novel insights into how mitochondrial dysfunction may cause pancreatic β-cell failure. In addition, the results will stimulate new thinking in the intersecting fields of mitochondrial dynamics and bioenergetics, as treatment of defective dynamics in mitochondrial diseases appears to be possible by improving metabolism upstream of mitochondria.